Cannabidiol (CBD) has been tested on pancreatic cancer which is almost untreatable, with chemotherapy achieving just a 7 per cent five-year survival rate. But when the substance is added, the rate trebles.

Researchers from Queen Mary University in London have so far tested cannabidiol only on laboratory mice, but if similar results can be seen in people, it could be "in use in cancer clinics almost immediately," said lead researcher Marco Falasca.

The risk is a little higher—at 28 per cent—among those who have the most severe form of periodontitis, and have lost all their teeth. Lung and colorectal cancers were the two most common cancers for people with bad gums, researchers at the Johns Hopkins Bloomberg School of Public Health found.